Research

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Radio Astronomy

We lead several MeerKAT projects and are deeply involved in a number of MeerKAT Legacy and Large Surveys.  These are both spectral line and continuum, and target our own Milky Way Galaxy out to high-redshift galaxies in the early Universe, with key objectives of understanding galaxy evolution across cosmic time and environment, the nature relativistic jets emanating from supermassive black holes, from event horizon scales to giant radio galaxies that span millions of light-years. 

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credit: SARAO

Gamma-ray astronomy

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credit: HESS

We are members of some of the largest international gamma-ray astronomy collaborations, including Fermi, H.E.S.S., and the CTA Consortium. Within H.E.S.S., we play a leading role in observation campaigns of the Large Magellanic Cloud and of starburst and Seyfert galaxies. Within Fermi, our interests lie in understanding blazar jets and constraining galaxy evolution through the cosmic gamma-ray horizon. We contribute to the Science Plan of the upcoming CTA array and simulations of the observability of source populations. We are also part of the CTA dark matter working group, assessing the potential of CTA as a dark matter probe.

Dark Matter

The nature of dark matter is one of the major unsolved questions in modern physics. It has mass, but we don’t know much about it. By bringing together radio, neutrino, and gamma-ray observations we can probe various models of particle dark matter in dwarf galaxies, radio galaxies, and galaxy clusters. The multi-frequency approach allows us to rule out models that are not compatible with a wider range of data in any dark matter dominated environment. We make use of powerful software written by Wits CfA members to produce highly competitive dark matter probes across the frequency bands. In addition to these searches, we also probe dark matter through the modelling of strong gravitational lens systems and neutral hydrogen galaxy rotation curves.  

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Neutrino Astronomy

Wits CfA is a member of KM3NeT, a next-generation neutrino telescope, to be located on the bed of the Mediterranean Sea. This facility will open a new window on the universe, enabling unprecedented discoveries in multi-messenger astrophysics. We are active in simulations of the observability of blazars and other extragalactic sources with the various stages and instruments of KM3NeT. Additionally, we work on methods of using neutrino observations to constrain leptophilic dark matter models, which are typically more challenging to probe via gamma-rays.

Algorithms and Software

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credit: KM3NeT

We lead the development of a number of software packages geared to advanced radio interferometry techniques, specifically toward MeerKAT and the Event Horizon Telescope. This includes advanced simulations, calibration, and Bayesian modelling of interferometric data. Our approach is to design projects in close collaboration with theorists and observers, as well as train up students with a keen awareness of how expertise in software and algorithms can advance their scientific objectives. 

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Very Long Baseline Inteferometry

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Very Long Baseline Interferometry (VLBI) is the technique of combining signals from antennas spread on (inter-)continental scales. This creates a virtual telescope almost the size of the Earth, enabling the sharpest images possible in astronomy. The Wits CfA carries out observations with several VLBI networks spread across the globe, aimed at understanding the evolution of jet-launching  black holes, and searching for binary supermassive black holes. Wits CfA members are also part of the Event Horizon Telescope Collaboration, who used a VLBI array observing light with a wavelength of 1 millimetre to capture the first image of a black hole.

credit: Laura Vertatschitsch

Galaxy Clusters

Galaxy clusters have masses greater than 100 trillion times that of the Sun, and are the most massive gravitationally collapsed objects in the Universe. They host hot gas atmospheres, with temperatures > 10 million degrees, that can be detected using X-ray and Sunyaev-Zel’dovich (SZ) effect observations. By measuring the number of massive clusters that there are in the Universe, we can learn about the properties of the mysterious dark matter and dark energy that makes up most of the energy density of the Universe. Clusters are also harsh environments for galaxies, and we can study the effects of interactions between galaxies and the gas in clusters to understand the effect on star formation and active galactic nuclei activity within galaxies. Wits CfA researchers are investigating all aspects of galaxy cluster evolution, using observations from across the electromagnetic spectrum.

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Credits: NASA, ESA, CSA, and STScI

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Telescopes

Members of the Wits CfA are active users of several Southern African facilities, including MeerKAT, SALT, HESS, and the nearby Hartebeesthoek Radio Astronomy Observatory, which forms part of several international VLBI networks. We have extensive formal links with local and international collaborations, including the MeerKAT Legacy / Large Survey Projects, SKA Science Working Groups, the Event Horizon Telescope Collaboration, HESS and CTA, KM3NeT, AGILE, Fermi, amongst others.

Image credit: CTA/ESO